linux-kernel - Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

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Message-ID: <CALMp9eQEjaaK=RDZ3OFL5+fq78nWRrpVO-KJ8ruosV9vWjfW6g@mail.gmail.com>
Date:   Thu, 15 Feb 2018 19:44:25 -0800
From:   Jim Mattson <jmattson@...gle.com>
To:     KarimAllah Ahmed <karahmed@...zon.de>
Cc:     kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Ashok Raj <ashok.raj@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dan Williams <dan.j.williams@...el.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH v6 2/5] KVM: x86: Add IBPB support

On Thu, Feb 1, 2018 at 1:59 PM, KarimAllah Ahmed <karahmed@...zon.de> wrote:

> @@ -3684,6 +3696,22 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
>         case MSR_IA32_TSC:
>                 kvm_write_tsc(vcpu, msr);
>                 break;
> +       case MSR_IA32_PRED_CMD:
> +               if (!msr->host_initiated &&
> +                   !guest_cpuid_has(vcpu, X86_FEATURE_IBPB))
> +                       return 1;
> +
> +               if (data & ~PRED_CMD_IBPB)
> +                       return 1;
> +
> +               if (!data)
> +                       break;
> +
> +               wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);

Should this be wrmsrl_safe? I don't see where we've verified host
support of this MSR.

> @@ -3342,6 +3369,34 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>         case MSR_IA32_TSC:
>                 kvm_write_tsc(vcpu, msr_info);
>                 break;
> +       case MSR_IA32_PRED_CMD:
> +               if (!msr_info->host_initiated &&
> +                   !guest_cpuid_has(vcpu, X86_FEATURE_IBPB) &&
> +                   !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL))
> +                       return 1;
> +
> +               if (data & ~PRED_CMD_IBPB)
> +                       return 1;
> +
> +               if (!data)
> +                       break;
> +
> +               wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);

And here too...wrmsrl_safe?